The present invention relates to a tool for rotary cutting machining with a tool body and a replaceable cutting head detachably attachable to the tool body. The invention also relates to a tool body and a cutting head included in such a tool.
A tool for rotary cutting machining is previously known from U.S. Pat. No. 5,988,953 A and U.S. Pat. No. 5,971,673 A. In this known tool, the mutual gripping surfaces of the tool body and the cutting head are conical and widen in the direction towards the rear end of the tool body and the cutting head, respectively, so as to thereby achieve a positive locking in axial direction between the tool body and the cutting head. This positive locking prevents the cutting head from being displaced in axial direction away from the tool body, for instance when the tool is pulled out of a bore drilled by means of the tool. A disadvantage with these conical gripping surfaces is that the tolerance requirements are high for these surfaces and that they are relatively complicated to achieve by, means of mechanical machining.
It is desirable to achieve a tool of the type mentioned by way of introduction with a new and favorable design.
According to an aspect of the present invention, a tool for rotary cutting machining comprises a tool body and a replaceable cutting head detachably attachable to the tool body, wherein:                the tool body at its front end has a coupling portion with two coupling legs projecting in the axial direction of the tool body and arranged on opposite sides of the center axis of the tool body;        the cutting head has a coupling portion, which is designed for engagement with the coupling portion of the tool body and which is receivable in a space between the coupling legs of the coupling portion of the tool body;        internal gripping surfaces are arranged in the space of the coupling portion of the tool body, which are designed for engagement with corresponding external gripping surfaces of the coupling portion of the cutting head;        the respective coupling leg is provided with a stop surface intended to transfer torque from the tool body to the cutting head, which stop surface is designed for abutment against a corresponding stop surface of the coupling portion of the cutting head and which extends in parallel with the center axis of the tool body or, starting out from its rear edge, is inclined forward in the intended machining direction of rotation of the tool body;        the coupling portion of the cutting head is turnable in the space of the coupling portion of the tool body about the center axis of the cutting head to and fro between a free position, in which the stop surfaces of the coupling portion of the cutting head do not abut against the corresponding stop surfaces of the coupling legs and the gripping surfaces of the cutting head are not in holding engagement with the corresponding gripping surfaces of the tool body, and an engagement position, in which the stop surfaces of the coupling portion of the cutting head abut against the corresponding stop surfaces of the coupling legs and the gripping surfaces of the cutting head are in holding engagement with the corresponding gripping surfaces of the tool body;        the respective coupling leg is provided with a shoulder protruding from the stop surface of the coupling leg; and        the cutting head is provided with two shoulders facing the front end of the cutting head and arranged on opposite sides of the center axis of the cutting head, which shoulders border on a respective one of the stop surfaces of the coupling portion of the cutting head and are arranged to extend in under a respective one of the shoulders of the coupling legs of the tool body when the coupling portion of the cutting head is in the engagement position in the space of the coupling portion of the tool body so as to thereby prevent the cutting head from being displaced in axial direction away from the tool body.        
In the tool according to the invention, the cutting head is prevented from being displaced in axial direction away from the tool body by means of a shoulder protruding from the torque carrying stop surface of the respective coupling leg, which shoulder is designed to extend out over a shoulder of the cutting head facing the front end of the cutting head, when the cutting head is attached to the tool body. The axial freedom of movement of the cutting head in relation to the tool body in the direction away from the tool body is consequently limited by these shoulders of the coupling legs of the tool body, and the cutting head is forced by these shoulders to accompany the tool body when the tool body is pulled in axial direction out of a bore drilled by means of the tool. With the solution according to the invention this axial locking of the cutting head to the tool body is achieved without requiring any conical sections in the mutual gripping surfaces of the tool body and the cutting head. These gripping surfaces can thereby be given a shape that is simplified and favorable with respect to the manufacturing of the tool body and the cutting head.
According to a favorable embodiment of the invention the stop surface of the respective coupling leg extends in parallel with the center axis of the tool body and the corresponding stop surface of the cutting head extends in parallel with the center axis of the cutting head. By letting the stop surfaces of the tool body be parallel with the center axis of the tool body, an achievement of these stop surfaces by mechanical machining of a blank prepared for the formation of a tool body is facilitated, and by letting the stop surfaces of the cutting head be parallel with the center axis of the cutting head, an achievement of these stop surfaces by mechanical machining of a blank prepared for the formation of a cutting head is facilitated.
According to another favorable embodiment of the invention, the angle between the stop surface of a coupling leg and the shoulder protruding from this stop surface is between 80-90°, preferably 90°. An angle of 90° is here particularly favorable, since this will give a right-angled design which facilitates the manufacturing of the tool body.
According to another favorable embodiment of the invention, there is in the normal state of the tool a clearance between the respective shoulder of the coupling legs and the corresponding shoulder of the cutting head when the cutting head is attached to the tool body. Hereby, there is no risk of wear between the mutually co-operating shoulders and the tolerance requirements on these shoulders will also be very low.
According to another favorable embodiment of the invention, each one of said shoulders of the cutting head is arranged on the upper side of the cutting head and preferably formed by a depression in a clearance surface arranged on the upper side of the cutting head. Hereby, the shoulders of the cutting head can be achieved in a simple manner and these shoulders will not interfere with the remaining design of the cutting head.
According to another favorable embodiment of the invention, the internal gripping surfaces of the coupling portion of the tool body are cylindrical and extend in parallel with the center axis of the tool body, and the external gripping surfaces of the coupling portion of the cutting head are cylindrical, extend in parallel with the center axis of the cutting head and have a radius which is larger than the radius of said internal gripping surfaces. By letting the gripping surfaces of the tool body be cylindrical and parallel with the center axis of the tool body, an achievement of these gripping surfaces by mechanical machining of a blank prepared for the formation of a tool body is facilitated, and by letting the gripping surfaces of the cutting head be cylindrical and parallel with the center axis of the cutting head, an achievement of these gripping surfaces by mechanical machining of a blank prepared for the formation of a cutting head is facilitated.
According to another favorable embodiment of the invention, the internal gripping surfaces of the coupling portion of the tool body are arranged on the inside of a respective one of said coupling legs at the level of the stop surface of the coupling leg, and the external gripping surfaces of the coupling portion of the cutting head are arranged at the level of the stop surfaces of the cutting head. Hereby, the coupling portion of the tool body and the coupling portion of the cutting head can be given a relatively compact design with a comparatively short extension in axial direction.
Other favorable features of the tool according to the invention will appear from the following description.
Aspects of the invention also relate to a tool body and to a cutting head.
Other favorable features of the tool body according to the invention and the cutting head according to the invention will appear from the following description.